Lost wax casting method



Jan. 28, 1969 B. STEELE LOST WAX CA STING METHOD filed Dec. 16, 1966 Sheet of 22 INVENTOR. BYRON STEELE A TTOH/VE'Y Jan; 28,, 1969 B. STEELE 3,424,226

Filed Dec. 16, 1966 Sheet 2 of 5 INVENT Ema/v .576 E ATTORNEY United States Patent 3,424,226 LOST WAX CASTING METHOD Byron Steele, 29 W. 9th St., New York, N.Y. 10011 Filed Dec. 16, 1966, Ser. No. 602,262 US. Cl. 164-28 6 Claims Int. Cl. B222 9/04, 9/02; B28b 7/34 The present invention relates to a novel lost wax method for making hollow metal castings from models of wax, clay, plaster, stone or other such material.

The lost wax process is, basically, a process whereby a removable duplicative material, namely wax, within a mold is replaced with metal of a permanent nature having the same configuration as the removable duplicative material. While application may be had to works of art duplicating an original sculpture-the process of the present invention provides castings of such great accuracy and faithfulness to the original or model that industrial applications wherein close tolerances must be maintained are contemplated.

The method taught herein is adaptable, as will hereinafter be shown, to various types of casting such as wherein (a) the original is of a destructible nature and need not be preserved and (b) the original is of a nondestructible nature and must be preserved. Examples of these categories may be (a) the original is made of wax which may be melted down, plastic which may be removed by a solvent, etc., or (b) the original is a material such as clay, stone or plaster which is not to be destroyed. In connection with this latter category, the method is applicable to originals of large size and scale. Hereinafter the original to be duplicated will be termed the model regardless of which category is involved.

In the drawing:

FIGURE 1 is a side view of a model showing core support pins, plug jackets and pin sleeves in place thereon.

FIGURE 2 is a side view of the primary investment which has been formed around the model of FIGURE 1.

FIGURE 3 is a fragmentary partial cross-sectional view taken across line 3-3 of FIGURE 2 showing a core support pin with plug jacket in place.

FIGURE 3A is the fragmentary cross-sectional view of the primary investment of FIGURE 3 with the core support pin, plug jacket andmodel removed therefrom.

FIGURE 4 is a fragmentary partial cross-sectional view taken across line 44 of FIGURE 2 showing a core support pin and a pin sleeve in place.

FIGURE 4A is the fragmentary cross-sectional view of the primary investment of FIGURE 4 with the core support pin and model removed therefrom.

FIGURE 5 is the fragmentary cross-sectional view of the primary investment of FIGURE 3 showing the wax shell and plug jacket in place.

FIGURE 6 is the fragmentary cross-sectional view of the primary investment of FIGURE 4 showing the wax shell, pin sleeve and dummy pin in place.

FIGURE 7 is the fragmentary cross-sectional view of the primary investment of FIGURE 4 showing the wax shell pin sleeve, core support pin and core in place.

FIGURE 8 is a portion of the fragmentary cross-sectional view of the primary investment of FIGURE 3 showing the wax shell, core and wax rods in place.

FIGURE 9 is a fragmentary partial cross-sectional view of the primary investment, secondary investment, wax shell, wax rods and core according to the present invention.

FIGURE 10 is the fragmentary view of FIGURE 9 after removal of the wax shell and wax in the gates and sprue.

FIGURE 11 is a side view of a plug jacket with a core support pin in place.

FIGURE 12 is a side view of a plug jacket with a pin molded in place. 1

3,424,226 Patented Jan. 28, 1969 FIGURE 13 is a top view of a plug jacket with a pin in. place.

FIGURE 14 is a bottom view as taken across line 14-l4 of FIGURE 11.

FIGURE 15 is a side view of a pin sleeve.

FIGURE 16 is a side view of a core support pin.

FIGURE 17 is a side view of a dummy pin.

Referring to the drawing, a model 10 may be made of any suitable material such as wax, clay, plaster, wood, stone or the like. At each of a number of various locations about the surface of model 10 is placed a core support pin 12, a view of which may be seen in FIGURE 16. Each core support pin 12 has a relatively thin, elongated tapered shank terminating in a relatively sharp point permitting such pin 12 to be pushed into model 10 with relative case. If model 10 is made of an impenetrable material, such as plaster or stone, into which core support pins 12 cannot be pushed, it may be necessary to drill holes therein to receive core support pins 12.

Each of the several core support pins 12 inserted partly into model 10 carries either a plug jacket 14 or a pin sleeve 16. Each plug jacket 14, which may be formed of any suitable material such as plastic, rubber or metal, has a body portion 14a of circular cross-section, the diameter of which becomes smaller as body portion 14a tapers to meet a relatively smaller end portion 14b having a square cross-section and ending in a bottom surface 140. Bottom surface of each plug jacket 14 is placed in contact with model 10 and may be shaped so as to follow the contour of model 10 at the area of contact. A central hole 14d is provided for insertion of a pin. Each pin sleeve 16 has a central tube 16a which may be made, for example, of copper alloy tubing, and several outwardly extending wire stabilizers 16b.

There is now formed about model 10 the primary investment 20. The inner surface 22 of primary investment 20 is made to contact and to follow faithfully the contour of model 10. Inner surface 22 forms the molding surface which determines the final shape and contour of the ultimate casting. Primary investment 20 is formed to a sufiicient thickness at least to cover the major portion of each of the plug jackets 14 and pin sleeves 16.

When primary investment 20 is completely formed and set, all core support pins 12 and some plug jackets are withdrawn and model 10 is completely removed from primary investment 20. While normally removal of model 10 involves destruction thereof, for example, melting or burning out a wax model, there is described hereinbelow a method of forming a primary investment without injury or destruction of the model. In all cases the primary investment should be preserved.

All plug jacket and pin sleeve holes in primary investment 20, with the exception of such holes to be used for air displacement, are now filled. Each pin sleeve 16 not to be used for air displacement is filled with a dummy pin 24. Each hole in primary investment 20 formed by removal of a plug jacket 14 and to be used for air displacement may be filled by reinserting a plug jacket which has no central hole 14d, or by placing other similar filler material in such hole after coating the surrounding surfaces thereof with a releasing agent to permit subsequent removal of the filler material. Dummy pins 24 are similar to core support pins 12 except that the former have blunt ends and are of the same lengths as the particular pin sleeve tube into which they may be placed.

Primary investment 20 may be inverted and is completely filled with molten wax or other such depositable and removable material. Unfilled holes in primary investment 20 permit the escape of trapped air and such holes are plugged as soon as air therein has been displaced and the molten wax begins filling such holes. The molten wax is permitted to solidify to the extent of forming a wax shell 26 of desired thickness adjacent to and completely covering inner surface 22, whereupon the remaining wax, still molten, is poured out of or otherwise removed from primary investment 20. The thickness 01f wax shell 26 determines the wall thickness of the final casting.

Dummy pins 24 are removed and core support pins 12 are inserted into pin sleeve tubes 16a. Other filler material, if used, is removed. All core support pins 12 pierce through wax shell 26. Some of such core support pins 12 are removed to provide air displacement passages through wax shell 26 and primary investment 20.

Investment material is placed inside primary investment 20 and wax shell 26 where it solidifies to form core 30. Air displacement holes are plugged with core support pins 12 as soon as all air has been displaced by the investment material. Core support pins 12 extend from primary investment 20 through wax shell 26 into core 30. FIGURE 7 shows the primary investment 20 and core 30 separated by wax shell 26 configuration which exists at this step of the instant process.

Selected plug jackets 14 are removed from primary investment 20 exposing wax shell 26 at such places. Wax rods 32a are placed in the holes thus formed in primary investment 20 and are attached, as by fusing, to wax shell 26. Wax rods 32a are cylinders of wax which are somewhat longer than the thickness of primary investment 20. Wax rods 32b are similar in material and diameter to wax rods 32a, but are of sufiicient length to permit said wax rods 32b to be placed in approximately parallel relation to inner surface 22 and for each of such wax rods 32b to connect with several wax rods 32a and to extend upwardly and downwardly to a point above and to a point below the secondary investment to be described. Wax rods 32a and 32b are fused, welded or otherwise joined together at each point of mutual contact.

A refractory material, known as investment material, is placed about the entire outer surface of primary investment 20, is inserted into all holes which are formed by removal of the remaining plug jackets 14 not selected :as in the preceding paragraph and is inserted about wax rods 32a in all such other formed holes. This investment material entirely covers all remaining core support pins 12 and wax rods 32a and 32b except for the uppermost and lowermost portions of the latter rods 32b which are left exposed; upon drying and setting, the material forms secondary investment 40. Secondary investment 40 is accordingly provided with a system of interconnecting wax channels formed by wax rods 32a and 32b which exit to meet at a point above and at a point below secondary investment 40.

The entire unit, now consisting of secondary investment 40, primary investment 20, wax shell '26, core 30, wax rods 32a and 32b and various core support pins 12 in pin sleeves 16 is heated to melt out all wax therein, the wax flowing out of the exposed point below secondary investment 40. The result is the formation of sprues 42, gates 44 and a void or space 26a between core 30 and inner surface 22 formerly occupied by wax shell 26. Sprues 42 and gates 44 form interconnecting passageways in secondary investment 40 which provide communication between space 26a and the outside, the passageways meeting at the outside surface of secondary investment 40 at the top and again at the bottom thereof. Core 30 is maintained securely in place relative to primary investment 20 by core support pins 12 which, having pierced through wax shell 26, are firmly embedded in core 30 on the one hand and secondary investment 40 on the other hand. After the wax has been melted out, the passageway opening at the bottom of secondary investment 40 is closed. The entire unit, which is called a mold, is now complete and is continuous.

Molten metal, or any other suitable material, is now poured into the complete mold and enters space 26a via sprues 42 and gates 44. Upon solidification of the metal, all investments-primary, secondary and core-are removed, leaving the final casting which is a duplicate, albeit hollow, of model 10. Metal which filled sprues 42 and gates 44 is removed as by cutting it away from the final casting. Core support pins 12 are withdrawn from the final casting and the remaining holes are, if necessary, filled.

In the event it is necessary to preserve model 10, primary investment 20 can be made in keyed sections as follows. The surface of model 10 is subdivided and pin sleeves 16, with a core support pin 12, are placed in each division, the core support pins 12 penetrating model 10. Pre-drilled holes may be necessary for this purpose. Wax rods 32a are attached to model 10. Plug jackets 14 are unnecessary for the keyed sections method in that the wax rods form the requisite holes in primary investment 20. Investment material is then placed against model 10 covering a given division. When dried and set the investment material becomes one section of what will be primary investment 20.

The section is removed from model 10 after first withdrawing core support pins 12 and the procedure is repeated for each of the other divisions on the surface of model 10. Sections of primary investment 20 may be keyed in any conventional manner, as by particular shape, by numbering or by other identifying means, so as to permit rapid and accurate assembly of the sections to form a complete primary investment 20. Sections may be welded to each other by use of investment material as a welding material, or any suitable adhesive or joining method may be utilized. Once fully assembled, primary investment 20 may be used in the manner specified above for a continuous primary investment.

The sectioned primary investment method of the paragraph last preceding may also be utilized if the model is of such large size, or has a particular shape or configuration, that a one-piece primary investment is not utilizable or is utilizable only with difiiculty.

While the foregoing is illustrative of preferred embodiments of the present invention, it is to be understood that other embodiments and modifications thereof may be provided within the broad spirit of the invention and the broad scope of the claims.

What is claimed is:

1. The process of casting a duplicate from a model, comprising the steps of:

(a) forming a primary investment, containing formed holes, about the model;

(b) separating the model from the primary investment;

(0) forming a shell of a removable duplicative material in the primary investment;

((1) forming a core in said shell and primary investmerit;

(e) placing removable rods in the formed holes in the primary investment and connecting said rods to said shell;

(f) forming a secondary investment about said primary investment, said secondary investment having interconnecting passageways formed therein;

(g) removing said shell and said rods from said core, primary investment and secondary investment; and

(h) casting the duplicate between the primary investrnent and core.

2. The process of casting a duplicate from a model in accordance with claim 1, additionally comprising the step of:

(a) securing the core in position relative to the primary investment.

3. The process of casting a duplicate from a model in accordance with claim 1, additionally comprising the step of:

(a) pinning the core to the primary investment to prevent relative movement therebetween.

4. The process of casting a duplicate from a model in accordance with claim 1, additionally comprising the step of:

(a) pinning the core to the primary investment to prevent relative movement therebetween by embed- 5 6 ding pins in the secondary investment, said pins pass- (b) assembling the keyed sections after removal from ing through and being supported -by the primary inthe model to form the primary investment. vestment by means of pin sleeves secured therein, References Cited and extending into said core. 5. The process of casting a duplicate from a model in 5 UNITED STATES PATENTS accordance with claim 1, additionally comprising the 3,063,113 11/1962 Operhall et a1. 16445 step of: 3,139,656 7/1964 Watts et al. 164246 X (a) forming holes in the primary investment by means 3,186,041 6/1965 Horton 164-25 of removable plug jackets, 3,336,970 8/ 1967 Watts et al 16425 6. The process of casting a duplicate from a model 10 in accordance with claim 1, wherein forming the primary WILLIAM sTEpHElrlsoN Pnmfm, Examme" JOHN S. BROWN, Asszstant Exammer.

investment comprises the steps of:

(a) forming investment material in individual keyed s L X R sections about the model; and 164 361; 249-85 

1. THE PROCESS OF CASTING A DUPLICATE FROM A MODEL, COMPRISING THE STEPS OF: (A) FORMING A PRIMARY INVESTMENT, CONTAINING A FORMED HOLES, ABOUT THE MODEL; (B) SEPARATING THE MODEL FROM THE PRIMARY INVESTMENT; (C) FORMING A SHELL OF A REMOVABLE DUPLICATIVE MATERIAL IN THE PRIMARY INVESTMENT; (D) FORMING A CORE IN SAID SHELL AND PRIMARY INVESTMENT; 